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Radiator Fan System: Inspection

WARNING: This page is about a different variant/trim than selected.

Operating condition: 

Radiator fan operates depending on the radiator fan operation mode related to engine coolant temperature or the radiator fan operation mode related to A/C compressor load, whichever is higher as an operation mode.

Diagnosis: 

Radiator main fan and radiator sub fan do not rotate under the above operating conditions.

  1. CHECK OPERATION OF RADIATOR FAN  .
    1. Install the delivery mode fuse.
    2. Turn the ignition switch to ON.
    3. Using the Subaru Select Monitor, perform the active test for the radiator fan relay.
      NOTE:
      • When performing the active test for the radiator fan relay using the Subaru Select Monitor, the radiator main fan and radiator sub fan will repeat low speed revolution → high speed revolution → OFF in this order.
      • For detailed operation procedures of Subaru Select Monitor 4, refer to "Application help".

    Do the radiator main fans and radiator sub fans rotate at low speed?

    Yes: Go to  2 .

    No: Go to  3 .

  2. CHECK OPERATION OF RADIATOR FAN  .

    Using the Subaru Select Monitor, perform the active test for the radiator fan relay.

    NOTE:
    • When performing the active test for the radiator fan relay using the Subaru Select Monitor, the radiator main fan and radiator sub fan will repeat low speed revolution → high speed revolution → OFF in this order.
    • For detailed operation procedures of Subaru Select Monitor 4, refer to "Application help".

    Do the radiator main fans and radiator sub fans rotate at high speed?

    Yes: Radiator main fan system is normal.

    No: Go to  27 .

  3. CHECK POWER SUPPLY TO SUB FAN RELAY  .
    1. Turn the ignition switch to OFF.
    2. Remove the sub fan relay.
    3. Measure the voltage between the sub fan relay terminal and chassis ground.

      Connector & terminal 

      (B48) No. 41 (+) - Chassis ground (-):

    Is the voltage 10 V or more?

    Yes: Go to  4 .

    No: Go to  5 .

  4. CHECK POWER SUPPLY TO SUB FAN RELAY  .
    1. Turn the ignition switch to ON.
    2. Measure the voltage between the sub fan relay terminal and chassis ground.

      Connector & terminal 

      (B48) No. 38 (+) - Chassis ground (-):

    Is the voltage 10 V or more?

    Yes: Go to  7 .

    No: Go to  6 .

  5. CHECK FUSE  .
    1. Remove the fuse No. 31.
    2. Check the condition of fuse.

    Is the fuse blown out?

    Yes: Replace the fuse.

    No: Repair the power supply line.

  6. CHECK FUSE  .
    1. Turn the ignition switch to OFF.
    2. Remove the fuse No. 8.
    3. Check the condition of fuse.

    Is the fuse blown out?

    Yes: Replace the fuse.

    No: Repair the power supply line.

  7. CHECK SUB FAN RELAY  .

    Measure the resistance between sub fan relay switch terminals.

    Is the resistance 1 MΩ or more?

    Yes: Go to  8 .

    No: Replace the sub fan relay. Ref. to HVAC SYSTEM (HEATER, VENTILATOR AND A/C)>RELAY AND FUSE .

  8. CHECK SUB FAN RELAY  .
    1. Connect the battery to the terminal on the sub fan relay coil side.
    2. Measure the resistance between sub fan relay switch terminals.

    Is the resistance less than 1 Ω?

    Yes: Go to  9 .

    No: Replace the sub fan relay. Ref. to HVAC SYSTEM (HEATER, VENTILATOR AND A/C)>RELAY AND FUSE .

  9. CHECK HARNESS BETWEEN SUB FAN RELAY TERMINAL AND SUB FAN MOTOR CONNECTOR  .
    1. Turn the ignition switch to OFF.
    2. Disconnect the connector from the sub fan motor.
    3. Measure the resistance of harness between the sub fan relay terminal and sub fan motor connector.

      Connector & terminal 

      (B482) No. 1 - (B48) No. 40:

    Is the resistance less than 1 Ω?

    Yes: Go to  10 .

    No: Repair the open circuit of harness between sub fan relay terminal and sub fan motor connector.

  10. CHECK HARNESS BETWEEN SUB FAN MOTOR CONNECTOR AND MAIN FAN RELAY 2 CONNECTOR  .
    1. Remove the main fan relay 2.
    2. Measure the resistance of harness between sub fan motor connector and main fan relay 2 connector.

      Connector & terminal 

      (B482) No. 2 - (B48) No. 33:

    Is the resistance less than 1 Ω?

    Yes: Go to  11 .

    No: Repair the open circuit of the harness between sub fan motor connector and main fan relay 2 connector.

  11. CHECK FOR POOR CONTACT  .

    Check poor contact of sub fan motor connector.

    Is there poor contact of the sub fan motor connector?

    Yes: Repair the poor contact of sub fan motor connector.

    No: Go to  12 .

  12. CHECK SUB FAN MOTOR  .

    Connect the battery positive (+) terminal to terminal No. 1 of the sub fan motor, and the ground (-) terminal to terminal No. 2.

    Does the radiator sub fan rotate?

    Yes: Go to  13 .

    No: Replace the sub fan motor. Ref. to COOLING (H4DO)>Radiator Fan and Fan Motor Assembly .

  13. CHECK MAIN FAN RELAY 2  .

    Measure the resistance between terminals of main fan relay 2 switch (always ON side).

    Is the resistance less than 1 Ω?

    Yes: Go to  14 .

    No: Replace the main fan relay 2. Ref. to HVAC SYSTEM (HEATER, VENTILATOR AND A/C)>RELAY AND FUSE .

  14. CHECK HARNESS BETWEEN MAIN FAN RELAY 2 AND MAIN FAN MOTOR CONNECTOR  .
    1. Disconnect the connector from the main fan motor.
    2. Measure the resistance of the harness between main fan relay 2 terminal and main fan motor connector.

      Connector & terminal 

      (B473) No. 1 - (B48) No. 30:

    Is the resistance less than 1 Ω?

    Yes: Go to  15 .

    No: Repair the open circuit of the harness between main fan relay 2 terminal and main fan motor connector.

  15. CHECK GROUND CIRCUIT OF MAIN FAN MOTOR  .

    Measure the resistance between main fan motor connector and chassis ground.

    Connector & terminal 

    (B473) No. 2 - Chassis ground:

    Is the resistance less than 5 Ω?

    Yes: Go to  16 .

    No: Repair the open circuit of the harness between main fan motor connector and chassis ground.

  16. CHECK FOR POOR CONTACT  .

    Check poor contact of main fan motor connector.

    Is there poor contact of the main fan motor connector?

    Yes: Repair the poor contact of main fan motor connector.

    No: Go to  17 .

  17. CHECK MAIN FAN MOTOR  .

    Connect the battery positive (+) terminal to terminal No. 1 of the main fan motor, and the ground (-) terminal to terminal No. 2.

    Does the radiator main fan rotate?

    Yes: Go to  18 .

    No: Replace the main fan motor. Ref. to COOLING (H4DO)>Radiator Fan and Fan Motor Assembly .

  18. CHECK HARNESS BETWEEN SUB FAN RELAY AND ECM  .
    1. Disconnect the connector from ECM.
    2. Measure the resistance between the sub fan relay terminal and ECM connector.

      Connector & terminal 

      (B134) No. 37 - (B48) No. 39:

    Is the resistance less than 1 Ω?

    Yes: Go to  19 .

    No: Repair the open circuit of harness between sub fan relay terminal and ECM.

  19. CHECK FOR POOR CONTACT  .

    Check for poor contact of ECM connector.

    Is there poor contact of ECM connector?

    Yes: Repair the poor contact of ECM connector.

    No: Check the DTC. Repair the trouble cause. Ref. to ENGINE (DIAGNOSTICS) (H4DO)>READ DIAGNOSTIC TROUBLE CODE (DTC) .

  20. CHECK MAIN FAN RELAY 1  .
    1. Turn the ignition switch to OFF.
    2. Remove the main fan relay 1.
    3. Measure the resistance between terminals of main fan relay 1 switch.

    Is the resistance 1 MΩ or more?

    Yes: Go to  21 .

    No: Replace the main fan relay 1. Ref. to HVAC SYSTEM (HEATER, VENTILATOR AND A/C)>RELAY AND FUSE .

  21. CHECK MAIN FAN RELAY 1  .
    1. Connect the main fan relay 1 coil side terminal to the battery.
    2. Measure the resistance between terminals of main fan relay 1 switch.

    Is the resistance less than 1 Ω?

    Yes: Go to  22 .

    No: Replace the main fan relay 1. Ref. to HVAC SYSTEM (HEATER, VENTILATOR AND A/C)>RELAY AND FUSE .

  22. CHECK HARNESS BETWEEN MAIN FAN RELAY 1 AND MAIN FAN MOTOR CONNECTOR  .
    1. Disconnect the connector from the main fan motor.
    2. Measure the resistance of the harness between main fan relay 1 terminal and main fan motor connector.

      Connector & terminal 

      (B473) No. 1 - (B48) No. 36:

    Is the resistance less than 1 Ω?

    Yes: Go to  23 .

    No: Repair the open circuit of the harness between main fan relay 1 terminal and main fan motor connector.

  23. CHECK HARNESS BETWEEN MAIN FAN RELAY 1 AND ECM  .
    1. Disconnect the connector from ECM.
    2. Measure the resistance between main fan relay 1 terminal and ECM connector.

      Connector & terminal 

      (B134) No. 51 - (B48) No. 35:

    Is the resistance less than 1 Ω?

    Yes: Go to  24 .

    No: Repair the open circuit of the harness between main fan relay 1 terminal and ECM.

  24. CHECK HARNESS BETWEEN MAIN FAN RELAY 2 AND ECM  .

    Measure the resistance between main fan relay 2 terminal and ECM connector.

    Connector & terminal 

    (B134) No. 51 - (B48) No. 31:

    Is the resistance less than 1 Ω?

    Yes: Go to  25 .

    No: Repair the open circuit of the harness between main fan relay 2 terminal and ECM.

  25. CHECK FUSE  .
    1. Remove the fuse No. 3 and No. 32.
    2. Check the condition of fuse.

    Is the fuse blown out?

    Yes: Replace the fuse.

    No: Go to  26 .

  26. CHECK FOR POOR CONTACT  .

    Check for poor contact of ECM connector.

    Is there poor contact of ECM connector?

    Yes: Repair the poor contact of ECM connector.

    No: Repair the power supply circuit to the main fuse box.

  27. CHECK OPERATION OF RADIATOR FAN  .

    If the both fans do not rotate at high speed in the condition of step 2, check whether the radiator sub fan is rotating.

    Does the radiator sub fan rotate?

    Yes: Go to  20 .

    No: Go to  28 .

  28. CHECK GROUND CIRCUIT OF MAIN FAN RELAY 2  .
    1. Turn the ignition switch to OFF.
    2. Remove the main fan relay 2.
    3. Measure the resistance between main fan relay 2 terminal and chassis ground.

      Connector & terminal 

      (B48) No. 32 - Chassis ground:

    Is the resistance less than 1 Ω?

    Yes: Go to  29 .

    No: Repair the open circuit of harness between main fan relay 2 and chassis ground.

  29. CHECK POWER SUPPLY TO MAIN FAN RELAY 2  .
    1. Turn the ignition switch to ON.
    2. Measure the voltage between main fan relay 2 terminal and chassis ground.

      Connector & terminal 

      (B48) No. 29 (+) - Chassis ground (-):

    Is the voltage 10 V or more?

    Yes: Go to  30 .

    No: Repair the power supply line.

  30. CHECK MAIN FAN RELAY 2  .

    Measure the resistance between terminals of main fan relay 2 switch (always OFF side).

    Is the resistance 1 MΩ or more?

    Yes: Go to  31 .

    No: Replace the main fan relay 2. Ref. to HVAC SYSTEM (HEATER, VENTILATOR AND A/C)>RELAY AND FUSE .

  31. CHECK MAIN FAN RELAY 2  .
    1. Connect the main fan relay 2 coil side terminal to the battery.
    2. Measure the resistance between terminals of main fan relay 2 switch (always OFF side).

    Is the resistance less than 1 Ω?

    Yes: Go to  23 .

    No: Replace the main fan relay 2. Ref. to HVAC SYSTEM (HEATER, VENTILATOR AND A/C)>RELAY AND FUSE .

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